747-8i VNAV and VS speed out of control

User Support Hub Aircraft & Systems
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1

Randomly the aircraft will just plummet and fall into rapid descent mode. Manual flight is the only option when this occurs.
This is with fmc setup correctly, auto throttle activated. Ap activated.
Is there something I am missing here?

2

That’s not enough information to help you. What exactly is your sequence of how you activate autopilot and autothrottle? What modes are enabled?

3

I set altitude and speed on the icas and alt dials.
Enable flight directors. I take off manually then hit lnav and vnav buttons then enable auto throttle and finally hit the ap button. Vnav tends to fail straight away and the plane descends rapidly. So I use vspeed to ascend and descend but all of a sudden this mode stopped working properly mid flight.

4

I suggest using the Salty 747 Mod. Whilst by no means perfect it’s a vast improvement on the default 747

5

The flybywire a320 and a330 300 work fine.
I have the honeycomb bravo quadrant throttle plus the new airbus 319 a380 pack. No conflicts there apart from a bug where if I change speed or altitude in game and not using the throttles ap controls themselves the Ai doesn’t change speed or alt.

6

The policies between airlines on arming AP settings vary, but there are quite a few that require ALL of that to be armed on the ground. So, I suggest trying the following:

  1. Once your flight plan is entered, dial the altitude you were cleared for by ATC on MCP.
  2. Set your MCP speed to V2 (from your takeoff section in MCDU).
  3. Set heading to runway.
  4. ON THE GROUND: Enable FD, then VNAV and LNAV. Finally, make sure AT is armed.
  5. Once you are cleared for takeoff, apply power to the throttle, rotate at Vr and retract gear on positive rate climb. Now enable AP. Off you go. Retract flaps on schedule and you are set.

Using these procedures I have never had any issues with the 747.

2 Likes
7

With the new salty mod update to 0.3.0 the aircraft is working fine again.
No problems what so ever like I was having with erratic behavior.

8

The problem is VS is completely broken in the base plane, and even the mod has a hard time compensating for it.

9

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